The invention concerns a device for increasing the rotational speed of an exhaust gas turbo-charger on an internal combustion engine.
In order to increase the rotational speed of the supercharger turbine during acceleration from the part-load range, it is known from the category-forming U.S. Pat. No. 3,049,865 to branch off a bypass duct from the induction duct upstream of a blocking device. The bypass duct enters the induction duct downstream of the super charger, a device for reducing the cross-section through which flow can take place being arranged in the bypass duct. However, in this arrangement, it is a disadvantage that in the part-load range no fresh air enters the compressor, so that the temperature of the air which is situated in the compressor and which is constantly circulated increases, whereby overheating of the bearing of the compressor cannot be ruled out.
From West German Offenlegungsschrift No. 2,542,970, a super-charged internal-combustion engine is known, to which, under conditions of inadequate air supply, auxiliary air is supplied through the exhaust gas turbo-charger by means of an injector, which is acted upon with compressed air from a compressed air container and which is constructed as a Laval nozzle. The auxiliary air conveyed by the injector is supplied to the air charge duct downstream of the exhaust gas turbo-charger. However, in this arrangement it is a disadvantage that, during the supply of the auxiliary air, the power consumption of the compressor of the exhaust gas turbo-charger is not reduced.
A super charged internal-combustion engine with a duct bypassing the compressor is diclosed in West German Auslegeschrift No. 1,451,898. On the downstream side of the compressor, the air induction duct and the bypass duct are alternatively closed by a blocking valve. The actuation of the blocking valve takes place in dependence upon the rotational speed of the exhaust gas turbo-charger or upon the feed pressure. However, in this arrangement it is a disadvantage that, when the induction duct is blocked, the power consumption of the compressor is not reduced.
An exhaust gas turbo-charger on an internal combustion engine with an annular-shaped duct with variable guide vanes located in the region of the suction-side opening of the compressor is known from German Patent No. 1,291,943. A disadvantage of this arrangement, however, is that the extra ducting of the combustion air increases the flow resistance due to the duct and the guide vanes located within it, particularly in the full load operation of the internal combustion engine and that, in consequence, the efficiency of the exhaust gas turbo-charger is reduced. In addition, the construction and control of the adjustable guide vanes is found to be complicated and expensive.
An object of the invention is to reduce the power consumed by the compressor during idling and lower part-load operation of the internal combustion engine.
The invention achieves this object by providing an ejector type Laval nozzle in the bypass duct having an annulus communicated with the compressor gas duct to effectively evacuate the gas duct and increase the compressor speed.
In preferred embodiments unloaded non-return valves are provided respectively in the bypass duct downstream of the ejector nozzle and in the induction duct between the compressor outlet and the bypass inlets. In especially preferred embodiments an automatic control mechanism is provided for controlling a guide device to guide air to the bypass duct when the turbo charger rotational speed falls below a predetermined value.
The device according to the invention has the advantage that in those operating phases in which the internal combustion engine having an exhaust gas turbo-charger operates under suction, the power consumed by the compressor can be reduced by partial evacuation of the gas duct so that increased exhaust gas turbo-charger idling speed occurs at the same turbine power. In consequence, a higher charge pressure is available at the beginning of the supercharge operation. The unsteady region is passed through in a shorter period. Since flow only occurs through the device when it is required, there is no disadvantageous change to the flow resistance and to the efficiency of the exhaust gas turbo-charger in the upper part-load and full load range. Furthermore, no expensive control is needed for operating the simple maintenance-free device because, using the guide device, it is only necessary to guide the induction airflow into the bypass duct.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.